1934 Act Registration No. 1-14700

SECURITIES AND EXCHANGE COMMISSION

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER
PURSUANT TO RULE 13a-16 OR 15d-16 OF
THE SECURITIES EXCHANGE ACT OF 1934

For the month of February 2005

Taiwan Semiconductor Manufacturing Company Ltd.

No. 8, Li-Hsin Rd. 6,
Hsinchu Science Park,
Taiwan
(Address of Principal Executive Offices)

     (Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.)

Form 20-F þ                    Form 40-F o

     (Indicate by check mark whether the registrant by furnishing the information contained in this form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.)

Yes o                    No þ

(If “Yes” is marked, indicated below the file number assigned to the registrant in connection with Rule 12g3-2(b): 82:           .)

TSMC Monthly Sales Report – January 2005

Hsinchu, Taiwan, R.O.C. — February 14, 2005 — Taiwan Semiconductor Manufacturing Company Ltd. (TSMC) (TAIEX: 2330, NYSE: TSM) today announced that net sales for January 2005 totaled NT$20,843 million, an increase of 8.8 percent over the same period last year. On a sequential basis, January 2005 sales increased 4.6 percent.

Ms. Lora Ho, TSMC spokesperson, vice president and chief financial officer, noted that TSMC’s January 2005 sales increased as a result of higher wafer shipments compared to December 2004.

Sales Report:

(Unit: NT$million, except for EPS)

* Year 2005 figures have not been audited.

TSMC Spokesperson:
Ms. Lora Ho
Vice President and CFO
Tel: 886-3-566-4602

TSMC Acting Spokesperson:
Mr. J.H. Tzeng
PR Department Manager, TSMC
Tel: 886-3-666-5028
Mobile: 0928-882607
Fax: 886-3-567-0121
E-Mail: jhtzeng@tsmc.com

For further information, please contact:
Richard C.Y. Chung
PR Principal Specialist, TSMC
Tel: 886-3-666-5038
Mobile: 886-911-258751
Fax: 886-3-567-0121
E-Mail: cychung@tsmc.com

Taiwan Semiconductor Manufacturing Company Limited
February 14, 2005

This is to report the changes or status of 1) sales volume, 2) funds lent to other parties, 3) endorsements and guarantees, and 4) financial derivative transactions for the period of January 2005.

1) Sales volume (in NT$: thousand)

2) Funds lent to other parties (in NT$: thousand)

* The deviation was due to the fluctuation in currency exchange rate.

3) Endorsements and guarantees (in NT$: thousand)

* The deviation was due to the fluctuation in currency exchange rate.

4) Financial derivative transactions (in thousand)

a-1. Hedging purpose (for assets / liabilities denominated in foreign currencies)

a-2. Hedging purpose (for the position of fixed rate liabilities / floating rate assets)

     b. Trading purpose: None.

SIGNATURES

     Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.